Re: enq: tx - contention on selects
Date: Tue, 16 Sep 2008 11:59:49 -0700 (PDT)
selects across db links can wait for TX locks (mode 4). This is the only instance in oracle where a select can be locked.
Since your problem is frequent, this could be a flaky network causing
a lot of distributed transactions to go into a pending state.
Once a transaction goes into a pending state, other sessions trying to
access that data may wait with TX mode 4.
You can monitor DBA_2PC_PENDING & DBA_2PC_NEIGHBORS.
srivenu Received on Tue Sep 16 2008 - 13:59:49 CDT